Stepping motors capable of inducing selected rotary motion and linear motion axially of the rotary motion are well known. Typically, such devices utilize a stator having zoned magnetic field producing means and an armature having portions, usually rings or splines, which may be aligned with the activated magnetic field of the selected zone of the stator. Thus, the armature may be rotated and or displaced axially by, in preferred embodiments, multiphase activation of the stator magnetic zones. U.S. Pat. No. 3,881,139 discloses such motors, as well as useful control systems for multiphase control of the stator magnetic zones. Other related art teachings of such devices include U.S. Pat. Nos. 3,394,295, 3,441,819, 3,453,510 and 3,745,433.
However, conventional stepping motors, such as those described by the above-identified patents, are adaptable to index one rotating member relative to another rotating member only at the expense of substantial rotating mass, i.e. rotation of the nominal stator members with the indexed armative member, with accompanying moving contact between electrical slip rings to provide electrical current to the rotating coils. As a consequence, such stepping motors, though operable in rotary devices to provide rotary and linear indexing between two rotating members, are unduly heavy in subject to wear, arcing, and electrical failure at the slip rings.